This invention is designed to be used by carpenters and carpenter's helpers in the residential and small commercial building construction trade, specifically in the installation of ¾″ by 4′ by 8′ tongue and groove sub-flooring of various materials, including plywood and pressed, particle board. These sheets or boards are installed with glue and nails on top of joists, frame members or timbers that create the “support” for the floor this sub-flooring becomes part of. Finished flooring is then installed on top of this sub-flooring. This process is fairly uniform throughout the industry in North America and elsewhere.
Each sheet of flooring has a groove along one 8′ edge routed into the ¾″ vertical surface (with the sheet oriented as it sits installed) longitudinally ⅜″ deep and ¼″ wide in the center of the surface causing this edge to be named the “female edge.” And on the opposite 8′ edge, the sheet has a tongue routed similarly and longitudinally in such a way as to enable it to fit perfectly into and against the “female edge” of another and separate sheet, and causing it to be called the “male edge.” When these two edges fit together with the sheets of sub-flooring sitting side by side and flat on straight and true supports they create a flat, smooth and sturdy sub-floor, ready to receive finished flooring. These “male” and “female” edges fit very snugly and require high impacting with a heavy tool such as a sledgehammer to make them joined in the finished position. The 4′ edge of each sheet is left square and smooth for it butts the next sheet beside it with a support running longitudinally and centered under each and every joint at that point. However, this joint [I will call it the “end joint”] must also be closed with an impact applied to the open 4′ edge.
A “protector block,” usually constructed of a scrap piece of 1½″ by 3½″ framing stock called “2×4” usually 8′ long, is rested on the supports and against the female edge of the sub-flooring sheet to be installed while this sheet is placed along side the female edge of a previous sheet which has been fastened permanently to the supports. The protector block avoids damage that would be caused by the sledgehammer directly contacting any of the edges of the sub-flooring. A carpenter uses the sledgehammer to impact the protector block which then impacts the sheet, causing it to join with the sheet before it. To close the end joint, the carpenter or helper must get on his knees, choke up on the sledge-hammer handle, much like you would with a baseball bat, and hold a separate protector block usually 4′ long against the open 4′ edge and impact it. By the nature of framing there are no supports to rest the shorter protector block on during the closing of the end joint.
Installing sub-flooring in this manner (Drawing 8/9) is considered by most carpenters and carpenters' helpers to be one of the most difficult and dangerous jobs, if not the most difficult and dangerous job, in this industry. The 8′ protector block must be held in place by the carpenter or helper placing the balls of both feet on it, leaving only the heels of his feet resting on the still unfastened sheet of sub-flooring being installed. At the same time he must lean his entire upper body out over open supports so that a horizontal impact can be applied against the protector block by swinging the sledgehammer under his upper body. The small of the back does almost all of the work. The dangerous balancing over open joists or timbers is stressful, with exposure to drops of as much as 16′ to the deck or floor below, adding strain to the hard work. And the difficulty of making accurate contact with the 2×4 protector block sometimes leads to off center hits on the impact surface causing the protector block to shatter, sometimes leading to injury. There have been many inventions over the years invented to improve this process, some of which I list below, however, do to shortcomings of diverse nature, none of these have been adopted nationwide, if at all. The choice by almost all carpenters, do to its simplicity, and the lack of many of the shortcomings of current new inventions, is still the plain sledgehammer bought at any hardware store or lumberyard. That is why I will call this use of the simple sledge-hammer (Drawing 8/9) the “prior method.” My invention has shown, by on the job testing of the prototype, that it greatly reduces the difficulty of the prior method and changes it. It also speeds it up, and shows none of the shortcomings of previous new inventions.